This proposal describes the continuation of the National Resource for Aplysia, whose overall goal is to provide consistently high-quality cultured sea hares Aplysia californica (and their cultured red algal food) to researchers. A. californica is an important non-vertebrate (Opisthobranch mollusk) model system for health- related research, primarily in the neurophysiology of behavior and learning. We will continue to produce animals for research and to conduct basic research aimed at exploring new model uses and at improving the resource. There are four sub-projects/specific aims: 1. Production - Sales of animals to researchers in the US and internationally is projected to continue at present levels of 25,000 to 30,000 animals per year. This resource makes available high-quality A. californica at all life stages from eggs through mature adults by rearing animals in carefully controlled laboratory conditions. All life-stages are available in sufficient quantities to meet user demand throughout the year, eliminating reliance on wild-collected animals which have limited seasonal availability and are of unknown age and health status. 2. Production research programs - The resource has been continuously improved over the past 12 years by research to optimize rearing conditions for most life stages of A. californica. The proposed research program will focus on measurement and improvement of egg quality. 3. Animal Health Monitoring - We will continue a monitoring program based on screening animal health parameters to assure rapid detection and complete documentation of any disease processes that might occur in any developmental stages of animals at the hatchery. Any disease syndromes and suspected pathogens observed will be investigated and appropriate control measures applied. 4. Developmental Neurophysiology - We will begin to develop Aplysia as an aging model by studying the changes in D-Asp- and other agonist-activated ionic currents that modulate sensory neuron input in the tail withdrawal reflex, using single cell voltage clamping and recording of the intact reflex. Through this combination of production and basic research, we will improve the model system and extend its usefulness to other areas of research. RELEVANCE (See instructions): The California sea hare, Aplysia californica, is a large marine snail with a very simple nervous system. The National Resource for Aplysia raises and ships 25,000 to 30,00 of these animals per year to labs in the US and around the world for conducting basic research in neurobiology and behavior. This proposal would continue the production of these animals and expand their usefulness concerning studies of aging and Alzheimer's disease.